51314-4288-17Cr Corrosion Resistant Alloy Cracking Behavior in Mildly Sour Production Environments

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Product Number: 51314-4288-SG

ISBN: 4288 2014 CP

Author: Sytze Huizinga

Publication Date: 2014

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17% Cr corrosion resistant alloys are available for use as tubing material in oil and gas production wells under mildly sour conditions. With field experience of these alloys and laboratory test data still limited an investigation was carried out into the sulfide stress cracking and chloride stress corrosion cracking behavior at a range of temperatures.Cracking tests were performed on tensile bars taken from 17Cr tubing material which were subjected to Cyclic Slow Strain Rate Testing as quoted in ISO 15156 part 2. Exposure conditions in terms of temperature H2S pH and salt concentration were selected to include both concentrated brine (as in formation water) and low pH aqueous solutions (as in condensing water). Corrosion testing consisted of autoclave coupon exposure in the higher temperature regime.Austenitic-ferritic duplex stainless steels in oil and gas production type environments are known to exhibit the highest susceptibility for corrosion cracking at an intermediate temperature regime. The present work showed that the highest susceptibility of the 17Cr alloy may also be at intermediate temperatures in this case around 60°C. This appears to be related to the better corrosion resistance of the material demonstrated in the autoclave exposure tests as compared to 13Cr alloys while at the same time the hydrogen controlled sulfide stress cracking mechanism still plays a role.Further characterization of cracking resistance in relation to metallography and corrosion resistance will aid understanding of the application boundaries of the 17Cr alloy.